1. Field of Invention
The present invention relates to a system and method for treating wastewater, and more particularly to a wastewater treatment system and method utilizing a walnut shell filter media.
2. Discussion of Related Art
Walnut shell filter media is known for its affinity for both water and oil, making it a desirable filter media and is typically used for the removal of oil from water and wastewater. Conventional walnut shell filters include pressurized deep bed applications in which the water is forced through a bed depth. Periodic backwashes are also routinely conducted to regenerate the bed. Typical backwash methods include expanding or turning the bed by imparting energy to the bed.
Conventional backwash systems include mechanical mixing and mechanical scrubbing with impellors and recycle lines, as well as the introduction of high velocity gas or high velocity water in a countercurrent direction. Mechanical systems used to backwash beds increase the initial costs of the system and may lead to increased maintenance costs to service mechanical seals. Recirculation of the bed also increases the initial and maintenance costs of the filter unit and increases the footprint of the filter unit with additional pumps for recirculation. The mechanical backwash methods also utilize backwash fluid to remove any oil and suspended solids released from the bed, which leads to the generation of significant amounts of backwash fluid. Similarly, the use of high velocity backwash liquid generates a large volume of backwash fluid. Conventional backwash systems are also known to create dead spots in which the filter media is not sufficiently turned and/or in which the backwash fluid does not reach, effectively leaving oil and suspended solids in the bed.
A need remains for a compact walnut shell filter media unit having a footprint sufficiently small to be used in offshore applications. Moreover, there is a need to reduce the amount of backwash water generated during backwash of the walnut shell filter unit and to reduce the number of dead spots which are not contacted by the backwash fluid.